1. Field of the Invention
This invention relates to a magnetic actuator for use in optical scanners or the like.
2. Prior Art
FIGS. 9 and 10 illustrate an example of the construction of the prior art actuator useful in the application concerned which is manufactured utilizing silicon micromachining technique as disclosed in FIGS. 11 and 12 of Japanese Patent Application Publication No. 6-180428. This actuator comprises a frame 11, a movable board 12 located in the frame, and a pair of torsion hinges 13 supporting and mounting the movable board 12 to the frame 11, all these parts being integrally formed by etching in silicon.
The frame 11 is mounted on a substrate 15 with an insulating spacer 14 interposed therebetween, the substrate 15 being formed with a pair of fixed electrodes 16 on the surface opposing the movable board 12.
The movable board 12 acts as a movable electrode, so that upon a voltage being applied between either one of the fixed electrodes 16 and the movable board 12 through the frame 11 and the torsion hinges 13, static electricity is produced between the two to electrostatically attract the movable board 12 to the fixed electrode 16 to pivot the board about an axis defined by the pair of torsion hinges 13.
In the electrostatically operated actuator, as shown in FIGS. 9 and 10, it is to be noted that as the angle of rotation of the movable board 12 is increased, the voltage required to rotate the board is increased. In other words, a very large driving voltage is required in order to provide a large angle of rotation (angle of actuation).
In addition, since the prior art actuator is configured to apply the driving voltage to the movable board 12 itself, it presented a problem in terms of reliability in that there is a possibility of failure in operation due to displacement of the charge, for example.